This invention relates to a fuel transfer manipulator for liquid metal cooled fast breeder nuclear reactors (LMFBR). The function of the manipulator is to transfer fuel assemblies from a fuel chute arising from the reactor vessel to and from a fuel chute arising from a fuel storage pit to facilitate passage of fuel assemblies therebetween during reactor refueling operations.
The fuel assemblies of LMFBRs are immersed in a liquid metal coolant, usually liquid sodium, which can burn if exposed to environmental oxygen. Consequently, the systems for removing and replacing the fuel assemblies from the reactor must do so while maintaining the assembly in a sealed and protected environment. The usual method is to hoist the assemblies to and from the nuclear reactor vessel and to and from the fuel storage pit via two fuel chutes. The chutes terminate at one end in a transfer chamber where the fuel assembly must be transferred from one chute to the other. The transfer chamber is normally filled with an inert gas such as Argon. Because the transfer chamber is open to the reactor and to the fuel storage pit during fuel transfers, the transfer chamber is considered to be a high radiation and high temperature area to which human access is restricted.
The transfer chamber must be a small size because of the gaseous inerting requirement and because of space limitations imposed by the proximity of other equipment.
The transfer manipulator might be a hoist mounted on a bridge trolley, but this solution does not easily match the required motion because the lifting of the hoist must be remotely coordinated with trolley movement. The manipulator might be a pendulum mounted hoist but this solution suggests a tall structure.
Consequently, it is desired to provide a transfer manipulator which is simple in operation and construction, suitable for long term use in high temperature, high radiation areas, and small in size.